1. Field of the Invention
The present invention relates to an electric charging system and an electric vehicle, and, in particular, to a technology that warns of a weld failure of a relay.
2. Description of the Related Art
In recent years, electric vehicles that are equipped with an electric motor for propulsion have been under development. The electric vehicle is equipped with an electric storage device such as battery. Upon charging the electric storage device, a power supply connector extending from an external electric charger is connected to a power receiving connector of the electric vehicle. Furthermore, in the field of hybrid electric vehicles that are equipped with an engine and an electric motor for propulsion, so called a plug-in type vehicle is under development whose electric storage device is charged with an external electric charger.
Since a terminal voltage of the electric storage device is applied to the power receiving connector provided to the electric vehicle, it is necessary to ensure safety during a charging operation that exposes the power receiving connector. Thus, a relay is provided to a current carrying line that connects the electric storage device and the power receiving connector. When the charging operation is not performed, the relay ic disconnected, thereby protecting the terminal voltage from being applied to the power receiving connector.
Since a large current is supplied to the relay thus provided on the current carrying line during charging, a weld failure may occur at the relay. Thus, an electric charging system is proposed that switches the relay to a disconnection state after charging is complete as well as monitors a voltage change due to the relay disconnection (see, for example, Japanese Unexamined Patent Application Publication No. 2010-238576). By using such an electric charging system, it is possible to detect a weld failure of the relay.
When a weld failure of the relay is detected, a terminal voltage of the electric storage device may be applied to the power receiving connector. Thus, it is necessary to warn an operator such as a driver. However, it is not desirable to continuously and unreasonably warn the operator when a weld failure of the relay is detected. For example, when a warning is continuously issued due to a weld failure and a new warning is further issued due to another failure, the operator may misunderstand the new failure. Therefore, it is necessary to properly issue a warning depending on a situation instead of issuing a warning simply according to a weld failure of the relay.